如何使用 LINQ 查询来计数指定词在字符串中的出现次数

此示例演示如何使用 LINQ 查询来计数指定词在字符串中的出现次数。请注意，若要执行计数，请先调用 Split 方法来创建词数组。Split 方法存在性能开销。如果对字符串执行的唯一操作是计数词，则您应考虑改用 Matches 或 IndexOf 方法。但是，如果性能不是关键问，或者您已拆分句子以对其执行其他类型的查询，则使用 LINQ 来计数词或短语同样有意义。 C# class CountWords { static void Main() { string text = @"Historically, the world of data and the world of objects" + @" have not been well integrated. Programmers work in C# or Visual Basic" + @" and also in SQL or XQuery. On the one side are concepts such as classes," + @" objects, fields, inheritance, and .NET Framework APIs. On the other side" + @" are tables, columns, rows, nodes, and separate languages for dealing with" + @" them. Data types often require translation between the two worlds; there are" + @" different standard functions. Because the object world has no notion of query, a" + @" query can only be represented as a string without compile-time type checking or" + @" IntelliSense support in the IDE. Transferring data from SQL tables or XML trees to" + @" objects in memory is often tedious and error-prone."; string searchTerm = "data"; //Convert the string into an array of words string[] source = text.Split(new char[] { '.', '?', '!', ' ', ';', ':', ',' }, StringSplitOptions.RemoveEmptyEntries); // Create and execute the query. It executes immediately // because a singleton value is produced. // Use ToLowerInvariant to match "data" and "Data" var matchQuery = from word in source where word.ToLowerInvariant() == searchTerm.ToLowerInvariant() select word; // Count the matches. int wordCount = matchQuery.Count(); Console.WriteLine("{0} occurrences(s) of the search term \"{1}\" were found.", wordCount, searchTerm); // Keep console window open in debug mode Console.WriteLine("Press any key to exit"); Console.ReadKey(); } } /* Output: 3 occurrences(s) of the search term "data" were found. */